Power gas generating assemblies



July 26, 1955 2,713,768

R. LIVINGSTON ET AL POWER GAS GENERATING ASSEMBLIES Filed March 3, 19502 SheetEwShGe'L l Invenlora ROBERT LIVINGSTON ALEXANDER CANTLAYHUTCHISON M 4a, v

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y 1955 R. LIVINGSTON ET AL 2,

POWER GAS GENERATING ASSEMBLIES Filed March a, 1950 2 Sheets-Sheet 2 I II I I I I I l2 7 8a a s I F164. F/GS. 2 F/66 I nventors ROBERT LIVINGSTON ALEXANDER CANTL AY HUTCHISON I torney:

United States Patent POWER GAS GENERATING ASSEMBLIES Robert Livingston,Prestwick, and Alexander Cantlay Hutchison, Saltcoats, Scotland,assignors to Imperial Chemical Industries Limited, a corporation ofGreat Britain Application March 3, 1950, Serial No. 147,412

Claims priority, application Great Britain April 14, 1949 4 Claims. (Cl.6035.6)

The present invention relates to a new or improved power gas-generatingassembly of separable construction and of the kind including a compactcharge of a solid composition of the kind which when its thermaldecomposition is initiated sustains said decomposition exothermicallyinto gaseous products without detonation, independently of thesurrounding atmosphere. The new or improved power gas-generatingassemblies include for instance rocket propulsion assemblies orassemblies capable of delivering a stream of the power gases underpressure to a prime mover such as a reciprocating engine or turbine.

In power gas-generating units for operating mechanical devices and someforms of rocket devices it is well known for the construction tocomprise a reaction chamber into which the solid gas-generating chargeis introduced and in which it is enclosed by the closure of a breechmember or the like, this chamber being a permanent part of the structureand, except in the case of projectiles, intended to be recharged by theinsertion of another expendable charge of the solid gas-generatingcomposition. The expendable charge thus inserted into the chamberfrequently comprises in addition to the compact solid composition anassociated envelope or sheath which may serve to protect it frommoisture or to influence the manner in which the decompositionpropagates itself, for instance by affording protection against thepropagation of the decomposition over some portion of the surface of thecompact composition. Usually such envelope or sheath associated with thecompact gas-generating composition is of a destructible nature, and if aportion of it is of such a nature as to remain undestroyed after thecomposition has been consumed this is Withdrawn from the interior of thereaction chamber before the next charge is inserted.

The object of the present invention is to produce an easily assembledpower gas-generating assembly by providing a non-expandable frame-workportion for gripping within it a simple expendable gas-generatingportion comprising a gas-generating charge capable of generating for afew seconds of a stream of gas at a predetermined pressure, which may beof the order of at least atmospheres, when initiated in saidnon-expendable frame-work portion but which provides no propulsiveeffect if agcidentally ignited when not in said frame-work portion.

A power gas-regenerating assembly according to the present inventioncomprises an expendable portion within a non-expendable frame-workportion wherein said expendable portion comprises an annular solidgas-generating charge having a tubular metal envelope or sheathextending beyond said charge and open at both ends and wherein saidnon-expendable frame-work portion comprises in separable combination asafety disc end plate wall member, a nozzle end wall member, and spacingrod members adapted to hold said end wall members at a predeterminedadjustable distance apart to grip said expendable portionlongitudinally.

Preferably the said annular solid gas-generating charge 2,713,?63Patented July 26, 1955 "ice is protected from decomposition along itslongitudinal surface by a sheath of heat insulating material interposedbetween it and the said metal tube.

It is also preferred that ignition means for initiating thedecomposition of the said annular solid gasgenerating charge should beaccommodated in the metal tube. Furthermore it is also desirable thatthe said ignition means should be situated at the end of said expendableportion intended to face the safety disc end plate wall member of saidnon-expendable frame-work portion.

In the preferred form of the power gas-generating assembly it isdesirable that the ends of the metal tube of the expendable portionshould be parallel and accurately squared and that the said end wallmembers of said non-expendable frame-work portion should be grooved soas to enable gas-tight joints to be formed with the ends of the metaltube of the expendable portion.

The expendable portion in the gas-generating assembly is either clampedbetween the two end wall members by the spacing rod members taking theform of adjustable bolts or by having the two ends wall members kept ata fixed distance apart by fixed spacing rod members and one of the saidend wall members so constructed that the portion which is to abut theexpendable portion is capable of being moved towards said expendableportion by means of a threaded ring in said wall member.

The rechargeable expendable portion of the assembly may be provided forstorage purposes with end caps to protect the charge of compactcomposition therein from moisture and from mechanical damage.

The invention is illustrated with reference to the diagrammatic drawingsaccompanying the specification in which Fig. 1 is an isometric view ofthe complete assembly partly broken to show the internal construction ofthe expendable portion, this assembly being suitable for use as a rocketmeans for assisting the propulsion of a vehicle such as a motor bicycle;Fig. 2 is a similar view of part of the permanent frame-work portion ofthe assembly shown in Fig. 1; Fig. 3 is a longitudinal axial section ofthe assembly shown in Fig. 1; Fig. 4 is a longitudinal axial section ofthe expendable portion of the assembly illustrated in Fig. 1 and Fig. 3;Figs. 5 and 6 are end caps for the portion illustrated in Fig. 4; Fig. 8is a detail of a nozzle bearing member constituting part of theretention means for the expendable portion of the apparatus, and Fig. 7is a detail of a screw-threaded member cooperating with the nozzlebearing member of Fig. 8 intended to be inserted into a threaded channelvisible in Fig. 2; Fig. 9 is a view of a broken portion of a gasdelivery tube member intended to be used instead of the nozzle bearingmember shown in Fig. 8 when the gases from the assembly are to be usedfor driving a prime mover such as a reciprocating engine or turbine.

In Figs. 1, 2 and 3 of the drawings 1 is a metal end plate memberaxially channelled and internally shouldered having an internal screwthread in the wider portion of its bore which is situated in aprojecting portion 3, as is best seen in Figs. 2 and 3. 2 is a groovedend plate member having an axial bore 5, opening out at a shoulder intoa wider and partly screw-threaded axial channel as is best seen in Fig.2 and Fig. 3. When the device is assembled a diaphragm rupturable at apredetermined internal pressure interposed between gaskets 6a and 6bresting on the said shoulder is retained by an internally member shownin Fig. 8 has been broken to reveal a a similar gasketted groove 15. 12is the wall of a gasdefiecting hood 9 retained on the remote side of theend plate member 2 by the nuts 11. 16 are shouldered spacing rodspassing through the end plate member 2 and located in the end platemember 1 and arranged so as to hold the end plates 1 and 2 accuratelyparallel and at a fixed distance apart. These are also retained by thenuts 11. 17 is the cylindrical metal retaining wall of the expendableportion of the charge illustrated in Fig. 4, 18 is a layer of bondedasbestos sheeting and 19 is an annular charge of a pulverulent mixturecomprising a nitrate of a nitrogen base and a sensitiser of the thermaldecomposition thereof compacted by compression against said layer withinsaid cylindrical metal wall and drilled out into annular form. The heatinsulating composition 18 is tightly crushed between the compactedcomposition and the wall 17 so that the annular charge 19 is securelylocated in fixed position. The ends of the cylinder 17 are accuratelysquared and its thickness is such that it can enter the grooves 8 and15. A space is left between the ends of the cylinder 17 and the ends ofthe asbestos sheeting 18 and the annular charge of compacted composition19 sufiicient to ensure that when the assembly is put together no partwill bear lengthwise on the latter. At one extremity of the channel 17where the annular charge 19 and its insulation 13 are further curtailedthere is also accommodated a cup 20 of easily deformable material suchas rnillboard whose rim abuts the end of the insulation 18, this cupcontaining a pellet of gunpowder 21 to the end of which is attached anelectric match-head 22 from which extend the short leads 2S and 24having terminals 25 and 26 at their ends. The end caps and 6 are ofrelatively thin metal plate and are an easy push fit over the ends ofthe metal cylinder 17.

The nozzle member as is best seen in Fig. 8 embodies a metal disc 27having a gasketted groove to which reference has already been made andhas internally threaded channel into which a venturi 14 externallythreaded at its narrow end is screwed to form a tight joint with theassistance of a gasket ring 28.

In the externally threaded retaining ring 13 illustrated in Fig. 7 andalso seen in Figs. 1 and 3, 29 are slots enabling this ring to bescrewed into threads 4 seen in Fig. 2 after insertion of the nozzlemember illustrated in Fig. 8. 27' and 27" are lugs enabling the assemblyto be attached to the frame of a vehicle.

In order to assemble the device the end caps are removed from the metalcylindrical wall 17 of one of the supply of expendable portions of theassembly and this portion of the assembly is then introduced into theportion illustrated in Fig. 2 through the threaded channel in theprojection 3 which is sufliciently broad to enable one end of saidexpendable portion to be brought up against the end plate member 2. Thatend of the cylinder 17 near which ignition elements 21 and 22 aresituated is then fitted carefully into the gasketted slots 8, and theportions of the leading wires with their terminals 25 and 26 external tothe cup are brought through a narrow channel provided in the end platemember 2 to the exterior thereof. The narrow channel is then sealed bypacking not shown. The nozzle member is then inserted through thechannel 4 and the gasketted groove 15 carefully fitted on to the otherend of the cylinder 17. The threaded ring 13 is then screwed into placeso as to bring pressure to bear on the grooved ring 27 and thus providea gas-tight joint between the end members and the cylindrical wall ofthe venturi-nozzle-vented reaction chamber thereby formed. The safetybursting disc 6 is adapted to rupture at a predetermined pressure inexcess of the working pressure which it is desired to maintain in thereaction chamber. When the terminals and 26 are connected to a source ofelectric current the match-head 22 is ignited and this ignites thegunpowder pellet 21 which in turn ignites the exposed portion of thesurface of the annular charge of compacted composition 19, so that theinner cylindrical surface thereof very rapidly becomes ignited by thehot gases passing through it and the gases escape under pressure throughthe venturi nozzle 14 delivering a thrust in the opposite direction. Forthe operation of a motor bicycle it may be desirable to have one or moreof these devices on each side of the rear wheel and to have the openmouth of the gas-deflecting hood directed downwardly so that should thesafety disc 6 become ruptured its remains and the hot gases therebyescaping through the channel 5 will be downwardly directed; and it willbe understood that when two of the devices me arranged in this way thelugs 27' and 27" will be arranged in mirror image relationship withrespect to the mouth of the gas-deflecting slot. When the device is onerequired for starting an engine or the like the grooved and gaskettedend of the gas delivery pipe is brought to bear on the end of the metalcylinder 17 in a simliar manner to that employed in the case of thenozzle member illustrated in Fig. 8. After the charge has been consumedthe retaining ring 13 is unscrewed, the nozzle member 14 removed and thetube 17 is removed. The remains of the ignition system may then bewithdrawn from which ever side of the end plate 2 is convenient. As willbe understood the tube 17 is undamaged and may be recharged, but therewill usually be provided a plurality of charged expendable portions ofthe assembly. As will be understood the gaskets and safety disc mayrequire to be replaced from time to time.

The advantages of the invention include the reduction in weight of thepermanent portion of the apparatus, which is especially important inconnection with vehicles for which rocket propulsion is onlyoccasionally required. There is also an overall reduction in weight inthat the cylinder 17 in conjunction with the small end caps provides theonly container required for each charge of gas-generating composition.It is a further advantage that the rechargeable container is not initself of the nature of a rocket, so that any accidental ignition of thecomposition will merely result in the light end caps being blown 011 andwill not involve a heavy article flying away. A further and veryimportant advantage in the case of rocket devices is that it facilitatesthe positioning of the igniting means so that the ignition is initiatedfrom the end remote from the nozzle, whereby the ignition over all theexposed surface of the annular compact charge of gas-generatingcomposition is assisted by the direction of the flow of the gases. Theremoval of the remains of the igniting elements is also rendered veryeasy since the withdrawal of the tubular wall from its seating leavesthem exposed and accessible.

What we claim is:

1. A power gas-generating assembly comprising an expendable chargeportion including an annular solid gasgenerating charge, a sheath ofheat insulating material contingent with and surrounding said charge,and a metal tube contingent with and surrounding said sheath ofinsulating material, said metal tube extending beyond said charge andbeing open at both ends, a reusable rame portion for receivingsuccessive expendable charge portions therein, said frame portionincluding a first end plate wall, a second end plate wall, rod meansextending betwen said end plate walls for maintaining them in spacedrelation, said second end plate wall having an opening therein of a sizesufficient to permit said expendable charge portion to pass axiallytherethrough, a member having an exhaust outlet therein, and means forconnecting said member with said second end plate wall and for movingsaid member axially into engagement with the adjacent open end of saidmetal tube until the opposite open end of the latter engages said firstend plate wall, said member, said second end plate wall, and said metaltube forming a combustion chamber within which said gas-generatingcharge is expended.

2. A power gas-generating assembly as claimed in claim 1 wherein thesaid expendable charge portion is provided with ignition means forinitiating the decomposition of the said annular solid gas-generatingcharge, said ignition means being disposed in the end of said expendablecharge portion intended to face the first end plate wall of saidreusable frame portion.

3. A power gas-generating assembly as claimed in claim 1 wherein theends of said metal tube are parallel and accurately squared and saidfirst end plate walls and member are grooved so as to enable gas-typejoints to be formed with the ends of the metal tube of said expendablecharge portion.

4. A power gas-generating assembly as claimed in claim 1 wherein saidfirst end plate wall is provided with a safety disk adapted to burst ata predetermined pressure.

References Cited in the file of this patent UNITED STATES PATENTS196,019 Hooper Oct. 9, 1877 6 Emery Dec. 6, Vautin Sept. 16, de GanahlSept. 24, Rutishauser et a1. Aug. 26, Skinner Aug. 10, Lubbock et a1.Aug. 24, Mace et a1 Nov. 30, Parsons Oct. 11, Lauritsen Sept. 2,MacDonald Oct. 14,

FOREIGN PATENTS Germany Sept. 6, France June 3,

OTHER REFERENCES Astronautics (No. 33), March 1936, pages 8 and 11.

